FIG. 1 shows a structure of a plasma processing apparatus 10 being a conventional substrate processing apparatus.
Referring to FIG. 1, the plasma processing apparatus 10 comprises a processing chamber 11 having a space 11a defined inside, and a holding table 13 provided in the processing chamber 11 for holding a processing substrate 12 by the use of an electrostatic chuck.
The space 11a in the processing chamber 11 is exhausted/decompressed by an exhaust appratus such as a vacuum pump through exhaust ports 11D formed at at least two positions, preferably at three or more positions, at regular intervals so as to surround the holding table 13, i.e. in a substantially axisymmetric relationship with respect to the processing substrate 12 on the holding table 13.
A microwave transmissive window 17 serving to transmit a microwave is provided at a portion, in the outer wall of the processing chamber 11, corresponding to the processing substrate 12 and a plasma gas supply ring 20 serving to introduce a plasma gas into the processing chamber 11 is inserted between the microwave transmissive window 17 and the processing chamber 11. The microwave transmissive window 17 and the plasma gas supply ring 20 form the outer wall of the processing chamber 11.
It is configured that the microwave transmissive window 17 has a stepped shape at its peripheral portion and the airtightness in the processing space 11a is ensured by engagement between the stepped shape and a stepped shape provided on the plasma gas supply ring 20 and further by a seal ring 16A.
The plasma gas is introduced into the plasma gas supply ring 20 from a plasma gas introduction port 20A and diffused into a gas groove 20B formed in an approximately annular shape. The plasma gas in the gas groove 20B is supplied to the space 11a through a plurality of plasma gas holes 20C communicating with the gas groove 20B.
On the microwave transmissive window 17 is provided a radial line slot antenna 30 comprising a disk-shaped slot plate 18 brought into tight contact with the microwave transmissive window 17 and formed with a number of slots, a disk-shaped antenna body 22 retaining the slot plate 18, and a phase delay plate 19 made of a low-loss dielectric material such as Al2O3, SiO2, or Si3N4 and held between the slot plate 18 and the antenna body 22. Further, it is configured that the airtightness is ensured by a seal ring 16B at an engaging portion between the radial line slot antenna 30 and the microwave transmissive window 17.
The radial line slot antenna 30 is mounted on the processing chamber 11 through the plasma gas supply ring 20 and a microwave having a frequency of 2.45 GHz is supplied to the radial line slot antenna 30 from an external microwave source (not shown) through a coaxial waveguide 21.
The supplied microwave is radiated into the processing chamber 11 through the slots of the slot plate 18 and the microwave transmissive window 17 to thereby excite a plasma in the plasma gas, supplied through the plasma gas supply ring 20, in the space 11a right under the microwave transmissive window 17.
Of the coaxial waveguide 21, an outer waveguide 21A is connected to the disk-shaped antenna body 22 and an inner conductor 21B is connected to the slot plate 18 through an opening portion formed in the phase delay plate 19. Accordingly, the microwave supplied to the coaxial waveguide 21A is radiated through the slots while proceeding radially between the antenna body 22 and the slot plate 18.
In the plasma processing apparatus 10, it is possible to carry out a plasma oxidation process, a plasma nitridation process, a plasma oxynitridation process, or a plasma CVD process and, by applying a radio-frequency voltage to the holding table 13 from a radio-frequency power supply 13A, it is also possible to perform reactive ion etching to the processing substrate 12.
Such a plasma processing apparatus is described, for example, in Japanese Unexamined Patent Application Publication (JP-A) No. 2002-299330.
However, for example, in the plasma processing apparatus 10, there are cases where contaminants enter at the time of the substrate processing to contaminate the processing substrate 12.
For example, typically, there are cases where gas generated from the seal rings 16A and 16B containing fluoro rubber or the like as a main component causes the contamination of the processing substrate 12.
Moisture, organic matter, and further metal or the like adhere to the surface of the seal rings 16A and 16B and moisture, organic matter, etc. also exist inside them. If these contaminants are released from the seal rings and such outgas adheres to the processing substrate 12 during the substrate processing, a serious problem arises, for example, in the semiconductor manufacturing process or the like.
Further, in the plasma processing apparatus 10 introducing the microwave, there have been cases where, for example, in the processing chamber 11, microwave electric fields are concentrated to corner portions or the like formed inside the processing chamber 11 to thereby cause abnormal discharge. A problem has arisen that when such abnormal discharge is generated, the substrate processing becomes unstable and, further, impurities containing metal, for example, are produced due to the abnormal discharge to thereby contaminate the processing substrate 12.
Further, when the film formation process is implemented in the plasma processing apparatus 10, deposits are deposited in the processing chamber 11. The deposits are removed by carrying out a cleaning process. However, a problem has arisen that those portions such as, for example, corners inside the processing chamber 11 where the cleaning is difficult exist in the processing chamber 11 and thus complete removal of the deposits is difficult so that the processing substrate 12 is contaminated by particles of the stripped deposits which were deposited in the processing chamber 11.
It is a general object of this invention to provide a substrate processing apparatus that solves the foregoing problems and enables clean substrate processing eliminating contamination of a processing substrate.
It is a specific object of this invention to enable clean substrate processing eliminating the influence of outgas released from a seal material of a seal ring, etc. in a substrate processing apparatus.
It is another object of this invention to eliminate abnormal discharge in a substrate processing apparatus to thereby enable stable and clean substrate processing.
It is another object of this invention to improve the cleaning in a substrate processing apparatus so as to completely remove deposits generated at the time of film formation, thereby enabling clean substrate processing free of the influence of stripping of the deposits.